Dew point corrosion problem in catalytic cracking waste heat boilers
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During maintenance, it was found that the waste heat boiler suffered from severe flue gas dew point corrosion. How can this problem of flue gas dew point corrosion be prevented?
The feed water heat exchanger is used to raise the feed water temperature above the dew point temperature. Choose a proper soot blower to reduce catalyst accumulation
1. Increase the exit temperature of the flue gas at the economizer section of the boiler by at least 200 degrees. 2. Use sulfur transfer agents. 3. Control the sulfur and nitrogen content in the feed oil
Conventional methods: 1. Increase the outlet temperature of the boiler feed water pump, for example by raising the temperature of the deaerator. 2. Increase the amount of flue gas to the total volume in the surplus boiler, for example by opening the butterfly valve at the inlet to the surplus boiler and closing the butterfly valve in the bypass circuit of the surplus boiler. 3. Reduce the heat taken from the coal-saving section, for example, by adjusting the span of the coal-saving section slightly. Radical solutions: 1. Cut out the coal-saving section – I have indeed seen this method used; the companies that adopted it were in a difficult situation. During several maintenance checks on that coal-saving section, severe corrosion was detected. Apart from the unavoidable objective constraints, every other solution was tried, but none worked. 2. Increase the flue gas temperature to that of the remaining boiler, such as by raising the temperature of the regenerator. This method is not easy to implement, as the influence factor oil ratio is an important parameter. Personal opinion, for reference only.
Right, increasing the superheating area to boost superheating might work too, just saying – it’s not necessarily true